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ORIGINAL: silvercoupe97

I know of the threads that you''''re talking about DSM, but they are inconclusive.  They start, argue, but no finishing conclusion with facts.

So, I say no to the EVO 4-9, but yes to the EVO 1-3 (since it''''s the same 4g63).  Keep in mind that the E3 uses a similar cam as the 1G.

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Defiant


Now that you''ve put into the ante, here''s the deal: think of yourself as a cam rocker roller. Sit in the roller, just like you''re sitting in a roller-coaster car. Stretching out in front of you is the track, and ahead of you is a hill that you''ll be going up and over. Oh, and the ride will be very, very fast. Since this isn''t a Ducati ride, nor a Mercedes M198 engine, we''ll be taking the retaining wheels off the bottoms of the trucks, counting only on gravity (the valve springs) to keep us down on the track.
As we approach the hill, which turns out to be much more steep that it looked like, the rise into the actual climb is tapered some so that our spines aren''t speared upward into our brain cases (although most still have enough room in there that damage would be minimal). Kind of like the way a driveway''s curb is cut down to near street-level, to save you denting your rims every time you head toward the garage. In the case of DSM valve assemblies, the acceleration ramp is made so that it gives the hydraulic lifter a chance to adjust whatever clearance may be in the valve actuation system, and to keep from slamming the rocker bearings and valve stem tip.
The acceleration away from the ground (cam circle center) keeps increasing as we near the crest of the hill. However, at the summit, we can''t be going so fast that we fly off the track (valve float), and the track is carefully designed to keep us just at the edge of flying-off.
As we reach zero gravity, the track starts to fall out from under us again. And again, the profile of the track is arranged so that the wheels never come free of the rails (and the valves and followers don''t float). It''s not the same shape as the up-side of the ride was, but we''re falling very quickly (the valve is closing). But we don''t want to drive off the curb and land hard, and we don''t want the valves to hammer-out the seats. So there''s another nice, smooth ramp to bring us back to ground level (cam circle base). This also is designed so that the fancy suspension under our roller-coaster car (hydraulic lifter) doesn''t bounce nor go soft. If the roller-coaster was a hardtail (solid lifters) it would have a different shape from the one we''re on. And oh, looky, another hill already. All this crap has to go on just the same, every time, up to seventy times [I]every second[/I]. No jostling the riders, no "getting air", no driving up over nor off the edge of the curb. Just nice and smooth, up and down, fully controlled against gravity (valve spring pressure) every last time.
So, what happens if we pick the coaster car up, turn it around and ride the track backward? Oh, we''ll still go up and down. The summit will be a bit iffy, because all the careful sculpturing that made sure we''d stay against the rails in the other direction is now tending to bump us clear of the rails at the summit, and the acceleration and deceleration ramps aren''t working with this suspension. The lifters are getting pumped-up and bled-down wrong, we''re getting air at the peak, and everyone''s starting to throw up.